Ummm, Rast...I think we're a bit confused about the differences in speeds...
IAS (Indicated airspeed)-what the guage reads
CAS (Calibrated Airspeed)-IAS corrected for installation errors and such (like when flap settings have an effect on the reading and stuff)
TAS (Ture Airspeed)-how fast you're actually going through the air. Basically, since the air is not always the same density (due to local atmospheric pressure, temperature...), the airspeed indicator doesn't always indicate correctly. At 25,000 feet on a hot day, there's a lot less air density with which to push on the bellows, thus creating a reading as it would at a lower speed at lower altitude... Think about it, it'll make sense (the same reason the A/C loses performance at altitude makes the IAS read low).
Groundspeed-how fast the aircraft moves across the ground. You use TAS and your course to figure this out by figuring int he winds aloft (direction and speed). You can figure that out geometrically, but I've got a handy flight computer (3 of em actually)...moot point in AH anyway, seeing no winds aloft...
blk (AT)
PS-IAS is what we fly by (duh). Basically, because the airplane will always stall at the same IAS in the same conditions (1 G, wings level...) since the thin air that would make it stall at a higher TAS is also affecting the airspeed indicator... Think about it...it'll make sense (I didn't totally get it until I was just about to solo)
